1. Field of the Invention
The present invention relates to a vacuum lifting device for lifting and handling of objects, comprising a suction tube suspended at an upper end, a suction cup fitted at a lower end of the suction tube, a low pressure generating device communicating with the inner of the suction tube, which is extensible and contractible in dependence on the vacuum prevailing in the suction tube, a valve house protruding laterally from the suction cup, the inner of which valve house communicates with the inner of the suction tube, and a valve device with a hand grip rotatably mounted on the valve house for adjustable opening and closing of at least one aperture in the valve house wall by means of a regulating device actuated by the hand grip and comprising a closing member movable in relation to the aperture.
2. Description of Related Art
Devices of this type are priorly known, for example from U.S. Pat. No. 5,934,723 disclosing a valve means, known per se in other connections, comprising a rotary valve disc provided with apertures, which valve disc is pressed against a fixed wall also provided with apertures, which are placed such, that at a turning of the valve disc a flow aperture is formed that varies from zero to maximum. A drawback with such a valve arrangement in a wall, behind which a considerable vacuum prevails, consists in that the valve disc in closed position is sucked firmly against the wall, so that a comparatively big power is required to turn the valve disc till a certain opening is achieved. A further drawback when using this valve arrangement for regulating the vacuum in a hoisting device consists in that it is not possible to achieve a flow aperture that is large enough for the suction cup to release an object sucked to the suction cup. In that case the valve arrangement has to be completed with a further valve device coupled to the valve arrangement, which opens a complementary flow aperture that is large enough, which constitutes an undesired complication.